With narcissism levels on the rise among college students, and kids everywhere growing up with inflated egos and deflated life prospects, it’s hard to make the case for giving kids yet more pats on the back. But a growing body of research suggests we still have much to learn from traditional societies where babies grow into resilient and caring adults through a steady diet of nurturing.

Jared Diamond’s new book, The World Until Yesterday, describes some of the lessons we can learn from today’s hunter-gatherer societies that most closely approximate the way people lived in our ancestral past. While they vary in important ways, most of these societies share a leisurely childhood where infants are constantly held by their mothers or other caretakers and where young children have enormous freedom to play.

These traditional practices are important to understand because many indices of poor health in children — such as obesity, depression, ADHD and teen suicide — have increased dramatically in the U.S. over the past 50 years. At the same time, play, which has wide-ranging cognitive, physical, emotional and social benefits, is under siege from shortsighted school policies, changes in family structure and technology use, and other 21st century pressures. Although it’s tricky to make causal leaps, evolutionary psychologist Peter Gray links the decline in play to a rise in children’s psychopathology via lost opportunities to make friends, learn self control, develop intrinsic motivation and other basic developmental functions.

According to Diamond, babies are nursed on demand in the hunter-gatherer world, are never left to cry (88% of !Kung baby cries are responded to within three seconds), and children exhibit few of the psychological scars of contemporary life. Loneliness and depression are virtually unheard of and children learn empathy through noncompetitive games and the care of younger siblings. Kids in traditional societies have few rules or expectations; in some hunter-gatherer societies, such as the !Kung and Aka Pygmy, young children are even indulged when they slap and insult their parents.

The nuclear family is much less important in hunter-gatherer societies too. Nonparental caregivers play a much bigger role in child care than in contemporary industrialized societies, usually starting immediately after birth. Diamond cites a study of the Efe people, whose infants were passed around among nonparental adults an average of eight times per hour.

Of course, we’ve heard many of these recommendations before: skin-to-skin “kangaroo” care helps premature infants grow. “Breast is best.” Co-sleeping has had its moment too. What’s new is the argument that our modern child-rearing practices are rubbing up against 6 million years of human evolution (when the protochimpanzee and protohuman lines first split apart). The fact of the matter is that babies really weren’t designed to sit in car seats for extended periods of time or to sleep alone in their own bedrooms. And they certainly didn’t evolve to compete with an iPhone for adult attention. The hue and cry over attachment parenting, with images of neurotic yuppies breast-feeding well into elementary school, obscures a basic reality: modern life is not really compatible with the healthy child development we evolved to have.

Why is it so hard to meet the needs of babies and young children? Most obviously, a child-centric approach to human development demands a lot of resources in industrialized societies where the nuclear family bears the burden of child rearing. On-demand breast feeding and 24/7 physical contact are costly luxuries for well-off families, and even where possible, many contemporary parents would sooner dig ditches than live in such constant proximity to their offspring. Our culture is organized around devices, such as baby monitors and strollers, that keep infants at arm’s length.

But there may be more than technology and economics at work. It’s hard to avoid the sense that all this, well, infantilizing is just a bridge too far. If children are losing their moral compass and failing to “launch” into adult roles these days, how can we justify further amplifying the period when our kids are most indulged?

It feels counterintuitive. But cuddling babies is not the same thing as coddling teenagers. Hunter-gatherer childhoods are easy and playful, but adolescents are expected to go out and hunt lions. We seem to have things backward in our contemporary world, pushing our very youngest to do things that don’t make neurological or developmental sense while asking relatively little of our older kids. Human beings are endlessly adaptable, and it’s unrealistic to think we could or should step back in time. But if we want to stop the current slide toward depressed, unhealthy young people, maybe we shouldn’t ignore 6 million years of evolution either.